Papers by Keyword: Direct Synthesis

Abstract: In this study Fe₂O₃/SBA-15 catalyst was synthesized via direct synthesis method under acidic conditions using triblock copolymer Pluronic P123 as template, tetraethyl orthosilicate as a silica source and Fe (NO₃)₃∙9H₂O as iron source. Template was removed using extraction and calcination. The obtained catalyst was characterized using XRD analysis, WDXRF spectroscopy, N₂ adsorption-desorption analysis and STEM–EDX measurements. Results of catalyst characterization showed that the synthesized Fe₂O₃/SBA-15 is mesoporous silica with 2D p6mm hexagonal mesostructure loaded with 15.6 wt.% Fe₂O₃. Average pore size was 6.95 nm, homogeneous immobilized Fe₂O₃ nanoparticles do not disrupt the porous hexagonal structure of the support.

Abstract: Direct synthesis controller design approach has serious limitations when it is applied to plant models that have more complex models and models involving time delays. In such cases the design becomes more cumbersome and the time delay appears in the denominator making it difficult to realize. In order to get simple realizable controllers approximations of plant model and time delays are done. This leads to controllers with non-optimal parameters. In this paper, a new approach for designing the controller by combining direct synthesis approach and system identification is presented. The controller is identified from the plant model and the desired closed-loop without the need for approximating the plant model and the time delay and ensures that the controller parameters are optimal.

Abstract: A CuZnAl-based hybrid material was prepared by co-precipitation impregnation method using the active components of methanol synthesis material and pseudo-boehmite as the precursors. The as-prepared material was evaluated for the direct synthesis of dimethyl ether (DME) from syngas in a pressurized continuous flow fixed-bed reactor system. It was revealed that the hybrid material showed high activity and selectivity after an induced period, i.e. the CO conversion and DME selectivity reached as high as 81% and 67%, respectively. Moreover, it was observed that there was only slight carbon which could be eliminated rather than graphite carbon deposited on the material after run for 150 h, indicating its good stability for the direct synthesis process .

Abstract: H₃PW₁₂O₄0/Ce_0.1Ti_0.9O₂ and imidazolium salt ionic liquid catalysts were prepared and applied to the direct synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide. The effect of reaction temperature, reaction time, pressure of carbon dioxide and amount of H₃PW₁₂O₄0/Ce_0.1Ti_0.9O₂ in the presence of ionic liquid are discussed. The results showed that H₃PW₁₂O₄0/Ce_0.1Ti_0.9O₂is an effective catalyst. The high selectivity and higher yield of DMC were achieved. The combination of imidazolium salt and H₃PW₁₂O₄0/Ce_0.1Ti_0.9O₂ could evidently improve the yield of the product. The maximum DMC yield reached up to 12.98 % in the presence of EMImCl at 140°C and 2.4 MPa.

Abstract: Effect of CuCl source and content on formation of triethoxysilane in the direct process is described and discussed. The two sources of CuCl and the contact masses from the reduction reaction by silicon and CuCl have been investigated by X-ray diffraction, scanning electron microscope and N₂ adsorption-desorption with a purpose of studying the reasons that different CuCl sources cause different reaction effect. We found Si-Cu intermetallics in proportion to the contact area between CuCl and Si. So CuCl with the characteristics of finer particles and high specific surface area is beneficial to form vast scale active Si-Cu intermetallics. The CuCl concentration on the performance of the catalytic reaction between silicon and ethanol was investigated by online gas chromatogram. The catalyst concentration greatly influences various aspects of the direct synthesis of triethoxysilane, including the induction time, the reaction rate, the selectivity and the silicon conversion. The reaction activity and yield of triethoxysilane increase as the catalyst concentration increases. However, the reaction selectivity decreases when the catalyst concentration is more than 5%, in this case the yield of triethoxysilane is slightly lower than 10% catalyst concentration.

Abstract: Sn-containing hydrotalcite-like compounds were prepared by three different methods such as (i) direct synthesis, (ii) ion-exchange and (iii) grafting. These catalysts were proved to have framework Sn species by powder X-ray diffraction (XRD) analysis and UV-vis spectroscopy. The catalysts prepared by three methods were found to be active and selective for the liquid phase Baeyer–Villiger (BV) oxidation of admantonone using hydrogen peroxide (H2O2) as an oxidant and acetonitrile as a solvent. The Sn-hydrotalcite-like catalysts prepared by ion-exchange method exhibited better catalytic performance than the catalysts prepared by other two methods. Among the ion-exchanged hydrotalacite-like catalysts, 3% Sn ion-exchanged hydrotalcite exhibited superior activity at 30% conversion and 100% selectivity.

Abstract: The aim of this work is to study the new method of direct synthesis of lead and iodine as the input material of PbI2. This method has not been studied for this material till now, and seems to be one of the new methods for preparation of the input material. The photoluminescence measurement and measurement of resistivity has been done and compared with the measurements done by precipitation and zone purification.